import java.util.*;
public class LinkedHash17c{
	public static void main(String args[]){
		LinkedHashSet<String> pc = new LinkedHashSet<String>();
		pc.add("RAM stick");
		pc.add("GPU");
		pc.add(null);
		pc.add("RAM stick");
		pc.add("Processor");
		Iterator<String> itr = pc.iterator();
		while(itr.hasNext()){
			System.out.println(itr.next());
		}
	}
}